Gate array LSI

Abstract: A gate array LSI having functional blocks formed by interconnecting a plurality of basic cells (10) arranged on a semiconductor substrate in matrix form and either signal conductive patterns (7) or first power conductive patterns (5). The first power conductive patterns (5) are disposed on the plurality of basic cells (10) arranged in line and are divided and disposed on the basic cells so that the signal conductive pattern (7) is interposed therebetween. It is therefore possible to improve the efficiency of wiring macrocells.

Description: This invention relates to a semiconductor integrated circuit, and particularly to a gate array LSI. As a conventional gate array LSI, there is known one disclosed in Japanese Patent Application Laid-Open Publication No. 3-69163. The gate array LSI is one of a type that a plurality of basic cells each comprised of an NMOSFET having an N-type diffused region and a PMOSFET having a P-type diffused region are arranged in matrix form. Further, the gate array LSI is provided with a dedicated signal conductive pattern or conductor used for a clock signal and a test facilitation circuit. The dedicated signal conductor is used to suppress or control a reduction in performance of the clock signal and facilitate a test. A functional block such as a NAND circuit, an OR circuit or the like has been constructed by interconnecting the dedicated signal conductor, basic cells and a plurality of macrocells corresponding to wiring patterns with each other. In the basic cells for the gate array LSI, basic cell patterns fabricated on a semiconductor substrate in advance and patterns for the signal conductor and a power conductive pattern or conductor have no symmetry in directions vertical and horizontal to the semiconductor substrate. It has thus been desirable to improve the efficiency of wiring the macrocells of the same patterns. In GB-A-2134708 there is described a distribution line arrangement primarily for VLSI chips in which the clock line is shielded by providing ground lines on either side. A similar arrangement is described in Patent Abstracts of Japan, Vol. 14, No. 216 (E-0924) in which the clock signal wiring is positioned between electric source wiring used to supply currents at different potentials. The present invention seeks to provide a gate array LSI capable of improving the efficiency of wiring macrocells. According to the invention, there is provided a gate array LSI having a semiconductor substrate on which a plurality of basic cells are arranged in a matrix, said gate array LSI comprising a first conductor for transmitting signals, two second conductors for supplying power and a third conductor for supplying power, wherein said third conductor is divided into two electrically connected lines, said first conductor being interposed between and parallel to said two lines, said gate array LSI being characterised in that said basic cells are arranged in pairs, in which the first basic cell of each pair comprises a first diffusion region, and the second basic cell of each pair comprises a second diffusion region, in that said first conductor is disposed over said first diffusion region in such a way that the first diffusion region is disposed symmetrically in relation to said first conductor, in that one of said two second conductors is disposed over said second diffusion region of the second basic cell of said pair of cells, in that the other of said two second conductors is disposed over a second diffusion region of the second basic cell of the next adjacent pair of basic cells, and in that said two second conductors are arranged parallel with one another with the first conductor arranged centrally therebetween. While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention, it is believed that the invention, the objects and features of the invention and further objects, features and advantages thereof will be better understood from the following description taken in connection with the accompanying drawings in which:- Figure 1 is a plan view showing basic cells which form a gate array LSI according to the present invention; and Figure 2 is a plan view illustrating a layout pattern of the gate array LSI shown in Figure 1, wherein the basic cells shown in Figure 1 are arranged in matrix form. In Fig. 1, reference numeral 1 indicates a first diffused region of a first conduction type (N type, for example), which is fabricated on the surface of an unillustrated semiconductor substrate (such as a silicon substrate). Reference numeral 2 indicates a second diffused region of a second conduction type (P type, for example). Reference numeral 3 indicates each of gate electrodes, which is composed of polysilicon or the like. Reference numeral 4 indicates each of gate connection regions, which provide electrical connections between the gate electrodes 3 and other signal conductive patterns or conductors or the like. A single basic cell 10 comprises the first diffused region 1 or the second diffused region 2, the two gate electrodes 3 and the two gate connection regions 4. The basic cell 10 is comprised of two series-connected FETs. Reference numeral 5 indicates each of first power conductive patterns or conductors used for the supply of a ground potential, which extends in a horizontal direction as seen in Fig. 1 and is disposed above the first diffused region 1 and the gate electrodes 3. The first power conductors comprise parallel-arranged conductors divided into two lines. Further, reference numeral 6 indicates a second power conductive pattern or conductor for the supply of a high potential (5V or the like, for example), which extends in the horizontal direction as viewed in Fig. 1 and is disposed above the second diffused region 2 and the gate electrodes 3. The second power conductor 6 is disposed in a substantially central position of a region where the second diffused region 2 and the gate electrodes 3 are provided. Furthermore, reference numeral 7 indicates a dedicated signal conductive pattern or conductor provided for a clock signal and a test facilitation circuit, which is disposed in a position where it is interposed between the two first power conductors 5 and is provided substantially parallel with the first power conductors 5. Reference numeral 8 indicates each of substrate electrodes fabricated on the surface of the semiconductor substrate to maintain the semiconductor substrate at a predetermined potential. The substrate electrode 8 comprises the semiconductor substrate or a high-density layer of a conduction type identical to a well region formed within the semiconductor substrate. In the illustrated embodiment, an unillustrated insulative film is interposed between the first diffused region 1, the second diffused region 2 and the gate electrodes 3, and the first power conductors 5, the second power conductor 6 and the signal conductor 7. Further, the two divided first power conductors 5 are electrically connected to a common potential (ground potential) through the insulative film at at least one point. The width of the first power conductor 5 may be substantially half that of the single second power conductor 6. Since the signal conductor 7 is not provided on the second diffused region 2 in advance, the second power conductor 6 is disposed on the center portion of the second diffused region 2 so as to have, on the second diffused region 2, a layout pattern symmetric with respect to the horizontal and vertical directions as seen on the semiconductor substrate (Fig. 1). Similarly, the two first power conductors 5 substantially parallel to the signal conductor 7 formed in the center of the first diffused region 1 are provided on the first diffused region 1 with the signal conductor 7 interposed therebetween to thereby create the symmetry of layout patterns or symmetrical layout patterns. In order to make the symmetry of the layout patterns, the distances between the signal conductor 7 and one of the two first power conductors 5 and between the signal conductor 7 and the other first power conductor 5 may be set so as to become equal to each other. In the present embodiment, the thicknesses of the first power conductor 5, the second power conductor 6 and the signal conductor 7 and the interval between each first power conductor 5 and the signal conductor 7 are respectively 2.8 µ m, 2.4 µ m, 6.8 µ m and 1.4 µ m. As shown in Fig. 1, the first power conductors 5, the second power conductor 6 and the signal conductor 7 are disposed over a plurality of basic cells arranged in the horizontal direction as seen in Fig. 1. Namely, the gate array LSI according to the present embodiment is constructed in such a manner that a plurality of basic cells 10 comprised of FETs that are active elements having the same patterns, are provided on the semiconductor substrate in matrix form and the first power conductors 5 divided into the two lines and the signal conductor 7 are provided on their corresponding basic cells 10 whereas the second power conductor 6 is provided on its corresponding basic cells 10. The relationship between the directivity of a macropattern and each basic cell shown in Fig. 1 will now be described below with reference to Fig. 2. Fig. 2 is a plan view showing a layout pattern of the gate array LSI in which the basic cells shown in Fig. 1 have been arranged in matrix form. The same elements of structure as those shown in Fig. 1 are identified by the same reference numerals. In Fig. 2, reference numeral 21 indicates each of typically-shown macrocells for respectively forming functional blocks by electrically interconnecting the gate connection regions 4 and the like and the signal conductors 7 and the like provided on the basic cells. The four macrocells shown in Fig. 2 respectively have the same wiring patterns. A symbol ┌F┘ marked on each macrocell 21 shows the direction of the macrocell 21, i.e., the direction of the same wiring pattern. The macrocell 21 is formed as a layer identical to other conductor or an upper layer conductor. The wiring width of each macrocell 21 is set so as to be narrower than that of each of the second power conductor 6 and the signal conductor 7. The macrocell 21 forms a functional block obtained by establishing direct electrical connections between the signal conductor 7, the first power conductors 5, etc. and the gate connection regions 4, the first diffused regions 1, etc. As shown in Fig. 2, the gate connection regions 4 and the like are provided as symmetrical patterns in such a manner that the signal conductor 7 and the second power conductor 6 respectively centrally provided on the first diffused region 1 and the second diffused region 2 are taken as the centers respectively. Thus, in order to create the same functional blocks, the same macropatterns 21 may be used so as to form four layouts or arrangements. According to the present embodiment as well, the patterns can be symmetrically set even from any basic cell because the two first power conductors 5 and the second power conductor 6 are alternately disposed on the plurality of basic cells. It is therefore possible to improve the efficiency of laying out the macrocells 21. Since the signal conductor 7 is interposed between the two first power conductors 5 each having a predetermined potential, an influence exerted over other signal by coupling noise can be reduced and a stable signal can be transmitted. Further, according to the present embodiment, the first power conductors 5 divided into the two lines and the substrate electrode 8 can be connected to one another at two intersections. The present invention is not necessarily limited to or by the preset embodiment. A potential to be supplied through each of the two divided first power conductors 5 may be a power supply potential (5V), for example. The number of the first power conductors 5 may be two or more. In this case, the number of the first power conductors to be divided must be an even number. Further, the same number of first power conductors must be provided on both side of the signal conductor 7.

Claims: A gate array LSI having a semiconductor substrate on which a plurality of basic cells (10) are arranged in a matrix, said gate array LSI comprising a first conductor (7) for transmitting signals, two second conductors (6) for supplying power and a third conductor (5) for supplying power, wherein said third conductor is divided into two electrically connected lines, said first conductor (7) being interposed between and parallel to said two lines, said gate array LSI being characterised in that said basic cells (10) are arranged in pairs, in which the first basic cell of each pair comprises a first diffusion region (1), and the second basic cell of each pair comprises a second diffusion region (2), in that said first conductor (7) is disposed over said first diffusion region (1) in such a way that the first diffusion region (1) is disposed symmetrically in relation to said first conductor (7), in that one of said two second conductors (6) is disposed over said second diffusion region (2) of the second basic cell of said pair of cells (10), in that the other of said two second conductors (6) is disposed over a second diffusion region (2) of the second basic cell of the next adjacent pair of basic cells (10), and in that said two second conductors (6) are arranged parallel with one another with the first conductor (7) arranged centrally therebetween. A gate array LSI according to either one of claims 1 or 2 wherein the first diffusion region (1) is of a first conduction type and the second diffusion region (2) is of a second diffusion type.

Inventors: AMIYA MICHIHIRO, INOUE TORU, TAKAHASHI TADAO, AMIYA, MICHIHIRO, INOUE, TORU, TAKAHASHI, TADAO, AMIYA, MICHIHIRO, C/O OKI ELECTRIC IND. CO. LTD., INOUE, TORU, C/O OKI ELECTRIC IND. CO. LTD., TAKAHASHI, TADAO, C/O OKI ELECTRIC IND. CO. LTD.
Applicants: OKI ELECTRIC IND CO LTD, OKI ELECTRIC INDUSTRY COMPANY, LIMITED
Application year: 1994
Main classification: H01L27
IPC codes: H01L27, H01L21, H01L23